a. Field of the Invention
This invention relates to methods for removing unreacted monomers from polymerization slurries.
B. Description of the Prior Art
In the manufacture of acrylic polymers to be used in forming filaments, it is necessary to remove polymer solids from a liquid phase which may be made up of unreacted monomers or a mixture of unreacted monomers and water. This can be achieved by passing the slurry downward through a column while countercurrently passing steam upward through the column to strip off unreacted monomers and/or water. After the water and unreacted monomers have been separated from the polymer solids, the polymer solids are dried for later use. In such later use, the dry polymer is dissolved in a solvent to form a spinning dope which is passed through a filter to a spinnerette. One of the problems involved with prior art processes is the fact degraded polymer will be formed in the system and this degraded polymer will not dissolve sufficiently in the solvent, remaining in solid form to clog the filter. This results in extremely short filter life. It has been found that as little as 0.07 weight percent of degraded polymer in the polymer going to make up the spinning dope will result in a 10 to 20 fold reduction in filter life.
It has been found that any polymer solids which may find their way into contact with the inner wall of the column may tend to cling and, under the temperatures involved, become degraded within a short time period. In this invention, degradation of polymer solids is prevented, so that filter life is greatly extended.